OTSwriter中，针对OTS中自增的主键给null值报脏数据错误


sql长这样
select user_id ,user_name ,operation ,null as auto_key, UNIX_TIMESTAMP(create_time) as create_time ,\nip ,`method` as methods,params ,\nUNIX_TIMESTAMP(update_time) as update_time from bos_log
writer中的key字段长这样

Reproduce the shown SQL and OTSwriter key configuration first, then trace OTSwriter's handling of a null value for an auto-increment primary key. Done means this case no longer reports dirty data and the resulting write behavior is verified.

Written by the indexing model from the issue text.